CAPI involves an interviewer reading items from a computer and allowing the respondent to make verbal responses that are entered directly into the computer by the interviewer. Both ACASI and CAPI eliminate a separate data entry process and may therefore reduce data errors. The survey interview included detailed questions about age, race, educational attainment, health status, engagement with medical care, current treatment regimen, and sexual and substance use patterns (see Table 1). It also included focused questions on attitudes about HIV transmission Smad2 signaling and treatment,

perceptions of the quality and availability of services and information provided at the Madison Clinic, each individual’s experience with his or her provider, self-esteem, VX809 perceptions of stigma, and treatment optimism. Use of legal and illegal substances was assessed over a 3-month recall period [23]. Participants were asked how often in the past 3 months they drank alcohol (daily, 2–6

times a week, once a week, 1–3 times per month, less than once a month, never, or prefer not to answer) and whether they had used crack cocaine, cocaine in other forms, methamphetamine or sildenafil in the last 3 months (yes/no). They were also asked whether they had injected drugs in the last 3 months (yes/no). Responses to each of these questions served as our substance use variables. The survey interview asked participants a variety of questions regarding beliefs about HIV infection, transmission and treatment. Additional questions focused on availability of information, resources and support at Madison Clinic. Three of the questions were intended to form a scale measuring behavioural optimism based on the availability of combination treatments (‘treatment optimism’) and another four were intended to form an ‘HIV Stigma Scale’ (see Table 2 for items and reliability analyses). Given the poor psychometric qualities of the HIV Stigma Scale, individual items, but not the combined scale, were used in the subsequent

analyses. The Vildagliptin survey interview also included a condensed version of a coping self-efficacy scale which was developed as a measure of people’s perceived ability to cope effectively with life challenges. The original scale showed good reliability and acceptable evidence of concurrent and predictive validity [24]. A detailed interview was developed to assess sexual behaviour over a 6-month recall period [25,26]. Separate but equivalent versions of questions were developed for men and women, each with language tailored to be consistent with the participant’s gender and sexual orientation. The interview began with an introduction and definition of sexual terms to minimize ambiguity.